1. Field of the Invention
The invention pertains to an x-ray examination apparatus including an x-ray source, an imaging arrangement including a radiation conversion means facing the x-ray source, for convening image carrying x-radiation into image carrying visible radiation, an image conversion means having a plurality of image sensors for converting the image carrying visible radiation formed by the radiation conversion means into an electrical signal, and a plurality of lenses aligned with the radiation conversion means, so that respective regions of the radiation conversion means are imaged on respective image sensors. The invention also relates to an imaging arrangement for use in an x-ray examination apparatus, and relates to a radiation conversion means for use in an x-ray apparatus.
2. Description of the Related Art
An x-ray examination apparatus of said kind is described in the U.S. Pat. No. 4,503,460.
An x-ray examination apparatus as described in the cited reference comprises multiple image conversion means in that a plurality of semiconductor image sensors and optical coupling means having a plurality of lenses are provided for imaging respective regions of an output screen of an x-ray image intensifier onto respective semiconductor image sensors.
Various radiological examination procedures require that low doses of radiation are administered to an object. In particular, this is the case when a medical examination procedure is performed in a fluoroscopy mode. The performance of an x-ray examination apparatus as described in the cited reference will not be fully satisfactory. The output screen of the image intensifier radiates its output light according substantially to Lambert's law. The area of the output screen is much larger than the area of a charge-coupled device according to presently available technology, therefore, optical coupling means are required for imaging regions of the output screen onto respective charge-coupled devices. According to the apparatus described in the cited reference, said optical coupling means consists of a plurality of lenses. Each of said lenses has a numerical aperture which is less than 1, or equivalently, its angle of acceptance is less than 90.degree.. The respective regions of the output screen of the image intensifier being much larger than an area of each of said respective charge-coupled devices, a considerable demagnification is required for each of said lenses. Hence, the optical efficiency of the optical coupling means is substantially reduced, so that the intensity of the light arriving at the charge-coupled devices is insufficient for performing accurate fluoroscopic examinations.